4
Short Reports

4.1 On Optimum Phasing for SIRTF

On February 2, the Committee on Astronomy and Astrophysics sent the following letter to NASA Chief Scientist France Cordova.

Thank you for visiting with the Committee on Astronomy and Astrophysics (CAA) at its September 1995 meeting. We appreciated your remarks on educating the public. This letter is in response to your question about optimum phasing for the Space Infrared Telescope Facility (SIRTF) with respect to operation of the other Great Observatories. We are basing our comments on the current NASA plan, according to which operation of the Advanced X-ray Astrophysics Facility (AXAF) will cease in late 2003 and that of the Hubble Space Telescope (HST) in 2005. The CAA considered this question at its meeting and afterward concluded the following points.

As you know, SIRTF will be able to detect sources several orders of magnitude fainter than those detected by any previous infrared mission. We anticipate discoveries that can only be guessed at now. Although a number of important questions remain regarding variable sources that would be addressed most effectively by using all of the Great Observatories simultaneously, the greatest need is to ensure use of AXAF and HST to observe sources revealed by SIRTF’s deep surveys.

To the extent possible, the astronomical community will optimize the SIRTF surveys so that areas on the sky previously observed by AXAF and HST are reobserved in the infrared without the need for any special time overlap between the missions. But because SIRTF will observe a larger volume of space than the other two observatories, the greatest scientific payoff will be realized by pursuing a strategy that allows as much time as possible for analyzing SIRTF data before AXAF or HST operation ceases. A year is the minimum amount of time needed to ensure that the sources requiring short-wavelength follow-up are identified and then scheduled for observation with AXAF and HST. A year is needed not only to understand the output of SIRTF but also to ensure that viewing constraints will not preclude pointing of the other observatories at the newly discovered sources. Thus, a SIRTF launch early in 2002, or preferably earlier, would be optimum. We further note that SIRTF data could be analyzed, at least in a preliminary fashion, on a more accelerated schedule than currently envisioned, but this could drive up the mission cost.

Please call on the CAA for any further advice that you might need on NASA space astronomy and astrophysics missions.

Signed by

Claude R.Canizares

Chair, Space Studies Board



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Space Studies Board: Annual Report 1996 4 Short Reports 4.1 On Optimum Phasing for SIRTF On February 2, the Committee on Astronomy and Astrophysics sent the following letter to NASA Chief Scientist France Cordova. Thank you for visiting with the Committee on Astronomy and Astrophysics (CAA) at its September 1995 meeting. We appreciated your remarks on educating the public. This letter is in response to your question about optimum phasing for the Space Infrared Telescope Facility (SIRTF) with respect to operation of the other Great Observatories. We are basing our comments on the current NASA plan, according to which operation of the Advanced X-ray Astrophysics Facility (AXAF) will cease in late 2003 and that of the Hubble Space Telescope (HST) in 2005. The CAA considered this question at its meeting and afterward concluded the following points. As you know, SIRTF will be able to detect sources several orders of magnitude fainter than those detected by any previous infrared mission. We anticipate discoveries that can only be guessed at now. Although a number of important questions remain regarding variable sources that would be addressed most effectively by using all of the Great Observatories simultaneously, the greatest need is to ensure use of AXAF and HST to observe sources revealed by SIRTF’s deep surveys. To the extent possible, the astronomical community will optimize the SIRTF surveys so that areas on the sky previously observed by AXAF and HST are reobserved in the infrared without the need for any special time overlap between the missions. But because SIRTF will observe a larger volume of space than the other two observatories, the greatest scientific payoff will be realized by pursuing a strategy that allows as much time as possible for analyzing SIRTF data before AXAF or HST operation ceases. A year is the minimum amount of time needed to ensure that the sources requiring short-wavelength follow-up are identified and then scheduled for observation with AXAF and HST. A year is needed not only to understand the output of SIRTF but also to ensure that viewing constraints will not preclude pointing of the other observatories at the newly discovered sources. Thus, a SIRTF launch early in 2002, or preferably earlier, would be optimum. We further note that SIRTF data could be analyzed, at least in a preliminary fashion, on a more accelerated schedule than currently envisioned, but this could drive up the mission cost. Please call on the CAA for any further advice that you might need on NASA space astronomy and astrophysics missions. Signed by Claude R.Canizares Chair, Space Studies Board

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Space Studies Board: Annual Report 1996 David N.Schramm Chair, Board on Physics and Astronomy Marc Davis Co-Chair, Committee on Astronomy and Astrophysics Marcia J.Rieke Co-Chair, Committee on Astronomy and Astrophysics

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Space Studies Board: Annual Report 1996 4.2 On Internet Access to Astronaut Biomedical Data On July 24, the Committee on Space Biology and Medicine sent the following letter to NASA Acting Associate Administrator for Life and Microgravity Sciences and Applications Arnauld Nicogossian. At the Space Studies Board’s meeting on June 12–14, 1996, at the Ames Research Center, it was brought to our attention that NASA is making plans to post on the Internet for public access biomedical data obtained from space shuttle crew members during flight. While sensitive to NASA’s worthy goal of making flight data accessible to qualified researchers, the Board questions the general usefulness of making this information public. In addition, the Board is concerned about privacy considerations related to the ethics of handling of data obtained from experiments on human subjects. Because of the small size of shuttle crews, merely withholding the names of individual subjects will not preserve anonymity. The Board is also concerned that, even if permission for such public release is sought from the individuals involved, a practice of posting biomedical data publicly may discourage voluntary participation by astronauts as subjects in future experimental protocols. In your letter of June 28, 1996, you recognized many of these concerns and noted that you have asked Dr. Baruch Brody, chair of the NASA Bioethics Task Force, and Dr. Lawrence Dietlein, chair of the Johnson Space Center Institutional Review Board, to review them. Note that the Institute of Medicine has recently issued guidelines in the related area of handling of patient data (Health Data in the Information Age: Use, Disclosure, and Privacy, National Academy Press, Washington, D.C., 1994). We will be very interested to hear the conclusions of the reviews that you have requested from your Bioethics Task Force and Institutional Review Board. Our Committee on Space Biology and Medicine next meets on September 26 and 27, 1996. We would like to suggest that the results of the reviews be briefed to the Committee for discussion at this meeting and that NASA suspend action on public Internet posting of the astronaut data until this discussion can take place. Signed by Claude R.Canizares Chair, Space Studies Board Mary Jane Osborn Chair, Committee on Space Biology and Medicine

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Space Studies Board: Annual Report 1996 4.3 On Scientific Assessment of NASA’s Solar System Exploration Roadmap On August 23, the Committee on Planetary and Lunar Exploration sent the following report to NASA Science Program Director for Solar System Exploration Jurgen Rahe. In your letter of March 26, 1996, you requested that the Committee on Planetary and Lunar Exploration (COMPLEX) assess NASA’s Solar System Exploration Roadmap1 and report on the degree to which the Roadmap is responsive to the scientific priorities outlined in past National Research Council (NRC) reports. COMPLEX understands that you need this assessment by September 1, 1996, because the Roadmap is an integral part of a new solar system exploration strategic plan to be developed by NASA this fall. As you requested, the assessment was conducted at COMPLEX’s June 24–28, 1996, meeting held at the National Academies’ Arnold and Mabel Beckman Center. The assessment was based on material sent to committee members for review prior to the meeting, extensive briefings by Dr. Larry Soderblom of the Roadmap development team, and subsequent discussions in executive session throughout the week of the meeting. COMPLEX finds the goals and objectives set forth in the Roadmap to be generally consistent with the recommendations and priorities contained in past NRC reports, including An Integrated Strategy for the Planetary Sciences: 1995–2010,2 The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution,3 and Origin and Evolution of Life—Implications for the Planets: A Scientific Strategy for the 1980s.4 Moreover, the fact that the Roadmap was developed jointly by scientists and technologists is a strength consistent with recommendations in the 1995 NRC report Managing the Space Sciences.5 COMPLEX’s general assessment of the Roadmap is that it outlines a rich and ambitious program of planetary exploration through the year 2012. In particular, COMPLEX commends the Roadmap development team for adopting an approach to planetary exploration advocated by the Integrated Strategy, that is, systematically addressing key physical and chemical processes rather than taking the more traditional approach of cataloging and classifying planetary bodies. It is, however, important for the Roadmap’s scientific objectives to be brought into sharper focus with some indication of priorities for study and critical measurements to be made. Although COMPLEX recognizes that NASA committees will be charged with identifying priority mission sets, it notes that the Roadmap, in its current form, provides no obvious framework within which such priorities can be set. COMPLEX also notes that the Integrated Strategy’s highest priorities for solar system exploration, i.e., intensive studies of comets, Mars, and the Jupiter system, are not singled out for special attention, although all are, admittedly, included in the Roadmap. Three other specific issues that COMPLEX wishes to raise here concern the quests related to human destiny and life’s origins and the issue of nonflight programs. The human destiny quest is disconnected from the actual proposed campaigns and their scientific objectives. The connection should be clearly stated in the Roadmap report. The quest regarding life’s origins is recognized as a high priority in previous NRC studies,6,7 but it is essential that the Roadmap’s stated expectations for fulfilling the quest not be exaggerated. This part of the Roadmap report should be carefully assessed to ensure that it rests on realistic statements. COMPLEX also notes that the Roadmap 1   Roadmap Development Team, Mission to the Solar System: Exploration and Discovery—A Mission and Technology Roadmap (Version A), Jet Propulsion Laboratory, Pasadena, California, June 21, 1996. 2   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994. 3   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990. 4   Space Studies Board, National Research Council, Origin and Evolution of Life—Implications for the Planets: A Scientific Strategy for the 1980s, National Academy Press, Washington, D.C., 1981. 5   Space Studies Board, National Research Council, Managing the Space Sciences, National Academy Press, Washington, D.C., 1995. 6   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994. 7   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990.

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Space Studies Board: Annual Report 1996 does not recognize the role of nonflight programs. Although their exclusion may have been a consequence of the Roadmap development team’s charter, it is clear that laboratory experiments, modeling, Earth- and space-based telescopic observations, and field studies are essential to an understanding of the solar system, as documented in NRC reports.8–10 Despite these shortcomings and other criticisms outlined in the accompanying Assessment, the program of planetary exploration described in the Roadmap has both significant potential for scientific discovery and the prospect of wide public appeal. The Space Studies Board and COMPLEX recognize that the Roadmap is an evolving document and that modifications will be made in response to changing circumstances and new developments (e.g., the recent announcement of the possible discovery of microfossils in a martian meteorite). Accordingly, we offer our services to you should you wish a review of a later draft of the Roadmap. In addition, the SSB and COMPLEX, in particular, look forward to the implementation of the Roadmap and will be pleased to review this phase of the solar system exploration program at an appropriate time. Signed by Claude R.Canizares Chair, Space Studies Board Ronald Greeley Chair, Committee on Planetary and Lunar Exploration REPORT At its June 24–28, 1996, meeting, the Space Studies Board’s Committee on Planetary and Lunar Exploration (COMPLEX), chaired by Ronald Greeley of Arizona State University, conducted an assessment of NASA’s Mission to the Solar System Roadmap report.11 This assessment was made at the specific request of Dr. Jurgen Rahe, NASA’s science program director for solar system exploration. The assessment includes consideration of the process by which the Roadmap was developed, comparison of the goals and objectives of the Roadmap with published National Research Council (NRC) recommendations, and suggestions for improving the Roadmap. Elements of the Roadmap The Roadmap concept is a new element in NASA’s strategic planning process. It is defined in the letter requesting this assessment as “a visionary but affordable outline of mission and technology development necessary to complete the overall survey of planetary bodies and to undertake the next evolutionary step of extensive in situ exploration and sample return from accessible bodies.” In the briefings COMPLEX received, it was emphasized that a key element of the Roadmap is the close coupling of scientific objectives for the exploration of the solar system with the technology development needed to meet those objectives. The report of the Roadmap development team identifies three major goals, or “quests,” for solar system exploration. Quest one is to chart human destiny in the solar system. Quest two is to seek the origin of life and its existence beyond Earth. Quest three is to explain the formation and evolution of the solar system and of Earth within it. 8   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994. 9   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990. 10   Space Science Board, National Research Council, Origin and Evolution of Life—Implications for the Planets: A Scientific Strategy for the 1980s, National Academy Press, Washington, D.C., 1981. 11   Roadmap Develpment Team, Mission to the Solar System: Exploration and Discovery—Mission and Technology Roadmap (Version A), Jet Propulsion Laboratory, Pasadena, California, June 21, 1996.

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Space Studies Board: Annual Report 1996 These quests would, according to the Roadmap, be addressed through five focused scientific themes, or “campaigns.” Each campaign contributes to the pursuit of one or more quests. For example, the campaign on the study of the evolution of Earthlike environments is relevant to the quests concerning both the origin of life and the formation and evolution of solar system objects. Although the Roadmap does not outline specific missions to implement the campaigns, it does include illustrative or “portrait” missions and the technologies enabling them. The intention of the Roadmap is to demonstrate that solar system exploration is a rich program with high scientific potential, wide public appeal, and opportunities for enhancing science education at all levels. Since specific mission sets are not defined and the costs of the portrait missions are not given, COMPLEX cannot comment on the affordability of the Roadmap. COMPLEX’s impression is that implementation of the programs outlined in the current Roadmap will far exceed the resources likely to be available for solar system exploration in the near future, and thus COMPLEX believes that priorities must be set. The Process of Developing the Roadmap COMPLEX was told that the Roadmap was the result of some 6 months of deliberations between some 50 planetary scientists and more than 50 engineers, technologists, and educators. Representatives from relevant advisory bodies, including the chairs of various NASA science working groups, participated in the development of the Roadmap to ensure that input from previous and ongoing studies related to solar system exploration was not overlooked. Additional input was received at a workshop open to the entire planetary science community. COMPLEX’s overall assessment of the process by which the Roadmap was developed is that it was fair and creditably reflects the caliber of its authors. This evaluation is based not only on the committee’s examination of the Roadmap report and the briefings received at the June meeting, but also on the first-hand experiences of COMPLEX’s chair as an observer at meetings of the Roadmap development team. The large development team and resulting diversity of opinions no doubt contributed to COMPLEX’s overall impression that the Roadmap tries too hard to satisfy everyone. Assessment of the Roadmap’s Quests In this section, COMPLEX comments on the Roadmap’s three quests and how they relate to priorities and recommendations contained in relevant NRC reports. Quest: Chart Human Destiny in the Solar System Implicit in this quest is the assumption that humans will eventually leave Earth and explore the solar system. If that is correct, then this quest is fundamental to planetary exploration. Moreover, the validity of this quest has been acknowledged in reports by both COMPLEX12 and the SSB’s Committee on Human Exploration (CHEX).13 The latter report, in particular, contains an extensive discussion of the role of scientists in human space exploration missions. As presented in the Roadmap, the human destiny quest does not appear to be geared primarily toward science, but rather toward the future of human space exploration. Yet, the related campaigns address scientific objectives. Thus, the link between this quest and the campaigns as described in the Roadmap should be strengthened. The relationship between the future habitability of Earth and possible hazards from impacts, in particular, should be explicitly addressed in the relevant campaigns. 12   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 17 and 193. 13   Space Studies Board, National Research Council, Scientific Opportunities in the Human Exploration of Space, National Academy Press, Washington, D.C., 1994.

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Space Studies Board: Annual Report 1996 Quest: Seek the Origin of Life and Its Existence Beyond Earth The search for life’s origins is given high priority in various NRC reports.14–16 The solar system affords numerous opportunities for studying biogenic processes, whether or not life actually exists, or has ever existed, on bodies other than Earth. Targets identified as high priorities in the Roadmap include the chemistry of Titan’s atmosphere, the hypothesized “ocean” beneath Europa’s surface ice, cometary dust, and rocks and soil returned from Mars. These are in accord with previous NRC recommendations.17 This quest’s emphasis on characterizing environments that have or have ever had water is appropriate. A weakness in this quest is the absence of any mention of laboratory studies of candidate early life processes. This aspect, emphasized in past NRC reports,18 includes the study of the origin and evolution of metabolism, replication, and RNA catalysis. If the search for life and associated chemistry on other planetary bodies is conducted without regard to these and other relevant processes, it is possible that critical evidence for life will be overlooked. Despite the potential for each single sample of Mars to provide compelling evidence about martian life, some aspects of this quest should be carefully supplemented if NASA is to lay the foundations for a more robust, longterm study of life beyond Earth. While searching for a fossil record on Mars may be a high priority, the possible discovery of microfossils on Mars must be linked to other evidence of life. In other words, the search for a fossil record on Mars should be tightly coupled with a search for more generic evidence of past life, such as the detection of chemical indicators or anomalous isotopic fractionations of carbon and sulfur. The general search for life’s origins is an important activity, and the Roadmap is correct in singling it out as a priority undertaking. However, the search must be undertaken in a realistic manner and with regard to current exobiological thinking.19 Ill-conceived and unrealistic priorities will only compromise the project in the long run. Quest: Explain the Formation and Evolution of the Solar System and Earth Within It The goal of understanding the formation and evolution of the solar system is fundamental to space science, as documented in numerous NRC reports.20,21 The campaigns to meet this quest provide focus for understanding many of the key aspects of how planets operate as complex physical and chemical systems, which is a high priority identified by COMPLEX.22 However, a flaw is the possible perception that this quest will be finished at the end of the period of time covered by the Roadmap, when, in fact, many questions will remain (and new questions will be raised) even if the Roadmap is fully implemented. Assessment of the Campaigns In this section COMPLEX assesses the various campaigns by which the Roadmap proposes that the three quests will be addressed. 14   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 14 and 33–69. 15   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990. 16   Space Science Board, National Research Council, Space Science in the Twenty-first Century—Planetary and Lunar Exploration, National Academy Press, Washington, D.C., 1988. 17   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, pp. 123–126. 18   For example, Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, pp. 123–126. 19   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 58–61. 20   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 13–14. 21   Space Science Board, National Research Council, Space Science in the Twenty-first Century—Planetary and Lunar Exploration, National Academy Press, Washington, D.C., 1988. 22   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 70–173.

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Space Studies Board: Annual Report 1996 Campaign: Building Blocks and Our Chemical Origins This campaign seeks to inventory the physical, chemical, and isotopic properties of materials that formed the solar system, to understand how these materials have evolved into the early planets, and to identify accessible resources for exploitation during human exploration missions. In general, the campaign is in keeping with COMPLEX’s past recommendations and priorities.23 Although the Roadmap identifies several key technologies necessary for outer solar system exploration, it should make a stronger tie between scientific studies of near-Earth objects and the human exploration of space. Moreover, the Roadmap does not appear to reflect the importance of interplanetary dust particles (or interstellar grains) for addressing such factors as planetary origins and formation of regolith, as has been suggested previously.24 Campaign: Prebiotic Chemistry in the Outer Solar System This campaign focuses on the satellites Europa and Titan and their potential as natural laboratories to understand how diverse environments can lead to the origin of life. Study of prebiotic organic chemical evolution on these bodies is consistent with NRC recommendations.25,26 This campaign provides opportunities to study prebiotic organic chemical evolution on a planetary scale in order to develop models of active regions in which chemical evolution could have occurred. Although results from this campaign could have wide public appeal, caution is dictated in two areas. First, the Roadmap strongly ties this activity to anticipated results from Galileo (for Europa) and Cassini (for Titan), and this dependence is accentuated by the decision to omit the study of other potential locations of prebiotic chemical evolution. Triton, in particular, would be a reasonable additional target to include in the future.27 Second, the campaign may promise too much about the potential for these satellites to tell us anything about life. Even if an understanding of prebiotic organic chemical evolution on a planetary scale is obtained from studies of bodies in the outer solar system, caution must be used in applying the results to Earth. COMPLEX has an additional concern about the use of the word “biological” to describe the “natural” laboratories on these moons or in the name of portrait missions (e.g., the Titan Biological Explorer). This usage is not justified and may prove to be a severe misdirection. It should be made clear that, for the present, Europa and Titan will serve as chemical rather than biological laboratories. Campaign: Evolution of Earthlike Environments This campaign focuses on the classic problem of understanding the evolution of the surfaces and atmospheres of the triad of terrestrial planets—Venus, Earth, and Mars. Its particular emphasis is on understanding how Mars and Venus have evolved so differently from Earth after presumably experiencing similar origins in the solar nebula. The role of water is central to this campaign, especially in the case of Mars, given its importance for the possible development of life and as a resource for human exploration missions. This campaign’s emphasis on the study of Mars’s climate, and the possibility that it is or was an abode of life, is consistent with COMPLEX’s previously published priorities.28 The further exploration of Venus has, however, not been given as high a priority by COMPLEX. 23   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 184–195. 24   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 11–69. 25   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 59. 26   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, pp. 21–77. 27   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 59–67. 28   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 184.

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Space Studies Board: Annual Report 1996 COMPLEX has attached very high priority to a better understanding of martian atmospheric circulation as the key component29,30 of the climate system and for comparative studies of atmospheric dynamics. Yet, this Roadmap campaign does not effectively address this key objective for Mars. Campaign: Formation and Dynamics of Earthlike Planets This campaign focuses on the internal dynamics of terrestrial planets. As such it is complementary to the campaign “Evolution of Earthlike Environments” (see above) and is consistent with COMPLEX’s recommendations.31 The interaction of the atmosphere and hydrosphere with the surface and interior of Earth plays a crucial role in our planet’s evolution. The role of water in these interactions is, undoubtedly, key to explaining why our planet is the only terrestrial body with plate tectonics. Consequently, it is difficult to discuss the dynamics of the solid Earth without taking this interaction into account. This campaign identifies all the inner planets, together with the Moon and Io, as pertinent objects to study. If the focus on Earthlike planets is to be adopted, then Europa should probably be added to the list because it is a rocky object with a volatile-rich surface and it has been geologically active in the recent past. Although COMPLEX has discussed the operation of planets from a broader perspective32 and has included essentially all planetary bodies, the Roadmap places relatively little emphasis on the workings of the interiors and surfaces of non-Earthlike planets. Important processes not identified in the Roadmap include mantle convection, which probably occurs in the interiors of icy and rocky satellites of the outer planets, and the dynamo action responsible for the outer planets’ magnetic fields.33 Because an understanding of the processes occurring in Earth benefits greatly from seeing how these same processes operate under different conditions, it would be a mistake to confine the study of these processes only to Earthlike planets as the Roadmap does. At the time of this assessment, this campaign’s “Goals and Expected Achievements” had not been articulated in the Roadmap, and so this critical aspect could not be reviewed by COMPLEX. Campaign: Astrophysical Analogs in the Solar System This campaign is essentially a study of basic physical and chemical processes occurring in planetary systems. Its objectives emphasize the fundamental processes that led to the formation and evolution of the solar system, yet the proposed execution of this campaign is a series of portrait missions focusing almost exclusively on the giant planets. Consequently, the campaign title is misleading. Of the portrait missions identified in the Roadmap, the outer planet missions are highly responsive to the priorities set by COMPLEX.34 The scientific objectives address key questions about atmospheric dynamics, chemical and isotopic composition, magnetospheric structure, and auroral phenomena, but the objectives neglect physical processes in the interiors of the giant planets. While the portrait mission to Mercury is a poor match to this campaign on the giant planets, such a mission is a previously identified priority of the space-physics community.35 29   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 192. 30   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996. 31   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 2 and 5. 32   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 5, 9, and 184. 33   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 132–136, 164, and 170–171. 34   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 170 and 193. 35   Space Studies Board, National Research Council, A Science Strategy for Space Physics, National Academy Press, Washington, D.C., 1995, p. 45.

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Space Studies Board: Annual Report 1996 Summary The Roadmap provides a potentially exciting and scientifically rewarding program of solar system exploration that is generally consistent with recommendations made in NRC reports. The Roadmap is responsive to COMPLEX’s existing advice except as follows: The scientific objectives in the Roadmap need to be brought into sharper focus with some indication of priorities for study and critical measurements to be made. Although it recognizes that NASA committees will be charged with identifying priority mission sets, COMPLEX notes that the Roadmap, in its current form, provides no obvious framework within which such priorities can be set. It also notes that COMPLEX’s highest priorities36 for solar system exploration, i.e., comets, Mars, and the Jupiter system, are not singled out for special attention, although all are included in the Roadmap. The Roadmap contains scientifically rewarding and potentially newsworthy exobiology investigations in several campaigns. Care must be taken by NASA not to exaggerate the benefits of specific missions to the search for life. To do so will undercut the significance of the science that can be achieved in missions to Europa and Mars and may damage the credibility of NASA’s missions with exobiological goals. The titles of two of the Roadmap’s campaigns should be modified to reflect their true content. “Astrophysical Analogs in the Solar System” is a misleading label for what is essentially a study of the physical and chemical processes in the giant planets. Perhaps a better title for this campaign is “Planetary Processes in Natural Laboratories.” The campaign dealing with the formation and dynamics of Earthlike planets should include “history” in its title. Various Earth-based investigations are essential to an understanding of the solar system. Laboratory experiments, modeling, Earth-based telescopic observations, and field study are excluded from the Roadmap but must be recognized as essential elements37 in solar system studies. The role of humans and the scientific goals in the human destiny quest should be identified and tied to the campaigns. Recent NRC reports (e.g., Scientific Opportunities in the Human Exploration of Space38) clearly outline the role and should be recognized in the Roadmap. The joint development of the Roadmap by scientists and technologists is a strength. However, there are some technological inconsistencies in the current version that need to be rectified. For example, the exploration of the Jupiter system emphasizes the use of radioisotope thermoelectric generators, whereas other missions to the outer planets focus on advanced solar cells and deployable solar concentrators. Another technology issue handled in an anomalous manner is communications. The Roadmap outlines various means for improving communication systems in spacecraft but pays no attention to the potential benefits obtained by improvements to the existing Deep Space Network. In conclusion, COMPLEX is generally positive about NASA’s Solar System Exploration Roadmap and commends the development team for synthesizing the study during today’s rapidly evolving budgetary and policy environment. 36   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994. 37   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 174–183. 38   Space Studies Board, National Research Council, Scientific Opportunities in the Human Exploration of Space, National Academy Press, Washington, D.C., 1994.

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Space Studies Board: Annual Report 1996 4.4 On the Planned National Space Biomedical Research Institute On October 10, the Committee on Space Biology and Medicine sent the following letter to Dr. Arnauld Nicogossian, NASA acting associate administrator for the Office of Life and Microgravity Sciences and Applications. During the past year and a half, NASA has been actively exploring the possibility of establishing independent science institutes that would operate cooperatively with the agency’s field centers. The objectives of these institutes have included strengthening the quality of NASA science and the relationship between NASA’s science programs and the university community. The Space Studies Board has maintained an active dialogue with agency officials as planning for these institutes has evolved and matured. In response to NASA requests, the Board issued short reports on the role of center science and scientists (Center Science Letter—March 29, 1995) and on the role and character of the proposed institutes themselves (Institutes Letter—August 11, 1995). In a comprehensive analysis of NASA science management, Managing the Space Sciences, (National Academy Press, Washington, D.C., 1995), the Board addressed a broad range of topics, many of which were related to the formation of the institutes. The Board notes that institute planning has been responsive to its guidance on the essential role of Headquarters in peer review and selection. It is our understanding now, however, that failure to obtain relief from certain federal employment regulations precludes the establishment of any of the proposed institutes save a biomedical institute associated with Johnson Space Center (JSC). In reviewing the Cooperative Agreement Notice (CAN) for the planned National Space Biomedical Research Institute (NSBRI) at JSC, the Board has identified a major concern. An essential requirement for the success of this proposed institute in strengthening programs to be hosted there is a scrupulous attention to the integrity of all aspects of program management. The Board is concerned about the following provision in the CAN: Management of the NASA Biomedical Research Program—NASA’s intent is for the Institute to manage (e.g., identify, prioritize, and recommend biomedical research thrusts and associated priorities, recommend research questions to be included in solicitations, and administer successful grants) the overall NASA biomedical Research and Analysis (R&A) effort. This approach would facilitate the execution of a comprehensive, and integrated research plan to support human space exploration, (p. 15) This provision is in direct conflict with the general principles guiding current planning for downsizing at NASA, namely that Headquarters will determine the “what” and “why” of the research program, with field centers determining the “how” (as stated, for example, in “FY 1996 Administrator’s Guidance,” February 2, 1996). The provision is at variance with CAN Table 2, which includes among “HQ/NASA HEDS Enterprise” responsibilities the following: Provide strategic planning, policy development… Provide program direction, advocacy, and oversight…. Appendix A of the CAN is consistent with this allocation of responsibilities from Table 2. The CAN provision also conflicts with major recommendations of the Board. In its Institutes Letter, the Board reserved certain management functions for discharge by Headquarters instead of by institutes or field centers, stating: Certain internal and external functions described in the Center Science Letter, such as participation in policy formulation and selection of external investigators, are properly the province of government employees, but should not be vested in field centers in order to avoid real or perceived conflicts of interest vis-à-vis outside scientific competitors. It is therefore the recommendation of the Board that these functions be retained by Headquarters, where they should be discharged by government employees. (Space Studies Board Annual Report—1995, National Academy Press, Washington, D.C., 1996, p. 88)

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Space Studies Board: Annual Report 1996 A recommendation in Managing the Space Sciences (p. 61) states further: Recommendation 5–12: Within NASA Headquarters, there must be a capable scientific staff to support management priority setting in order to help ensure compatibility of program content and science priorities. These scientists must also interface with field center managers and external investigators to ensure science program integrity. In numerous conversations with NASA officials, the Board has received assurances that the agency is fully in accord with these recommendations on research policy formulation and science selection. In a formal response to the second recommendation, Administrator Daniel Goldin (February 28, 1996) stated: Response to Recommendation 5–12: NASA believes that it has, at least in the past, been able to maintain a capable scientific staff. In the face of downsizing, NASA will need to rely increasingly on the external science community for its advice and participation in priority setting, scientific review of current programs, and strategic planning for future programs. This is understood to include both contributions by IPA (Intergovernmental Personnel Agreement) scientists within the Headquarters staff as well as by community members serving on volunteer panels advisory to this staff. In addition, Administrator Goldin gave very positive assurances on the primacy of Headquarters in setting research policy during an executive meeting with National Academy of Sciences President Bruce Alberts and the undersigned on April 30, 1996. Inasmuch as the NSBRI must be free to compete for research funds against other qualified institutions, and this competition must be perceived as equitable and wholly merit-based, the Board recommends revision of the cited language in the CAN to clearly reaffirm NASA’s intention to perform vital science policy and program definition functions itself, at Headquarters. The Board believes that continuing the practice of setting research directions and selecting science investigators and investigations at Headquarters, as well as maintaining the necessary qualified staff at Headquarters to carry out these functions, is vital if the agency is to achieve its goal of a first-rate life sciences research program. We look forward to working with you to strengthen the contributions of NSBRI planning and research to NASA’s science and exploration programs. Signed by Claude R.Canizares Chair, Space Studies Board Mary Jane Osborn Chair, Committee on Space Biology and Medicine

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Space Studies Board: Annual Report 1996 4.5 On NASA Mars Sample Return Mission Options On December 3, the Committee on Planetary and Lunar Exploration sent a letter report assessing Mars sample return planning to NASA Science Program Director for Solar System Exploration Jurgen Rahe. In your letter of September 17, 1996, you requested that the Committee on Planetary and Lunar Exploration (COMPLEX) assess NASA’s plans for Mars sample-return missions. COMPLEX understands that you need its remarks in early December to aid in policy decisions by the agency. As you requested, the assessment was conducted at COMPLEX’s October 16–18, 1996, meeting held at the National Research Council’s Georgetown offices. The assessment was based on “The Search for Evidence of Life on Mars,” a working paper drafted by NASA’s Mars Expeditions Strategy Group, guest lectures on the scientific goals for martian samples analyzed in laboratories on Earth, and presentations on NASA’s four possible mission options. NASA’s presentations emphasized that the exact sequence and details (e.g., payload mass and instrument complement of orbiters, and ranges and on-board analytical capabilities of rovers) of missions in all of the options are currently under development. Consequently, COMPLEX must defer a specific assessment of mission plans at this time. COMPLEX has, however, provided a general assessment based on recommendations made in previous National Research Council reports. As such, both COMPLEX and the Space Studies Board (SSB) regard this current document as one step in an iterative process that will continue with the evolution of NASA’s planning for the implementation of Mars sample-return missions. As you know, COMPLEX and the SSB have consistently emphasized the importance of an intensive study of Mars by spacecraft. An important element of such a program is the return of martian samples to Earth. COMPLEX continues to support this viewpoint. The primary objectives for sample-return missions have been clearly defined and prioritized by both COMPLEX and other groups (see attached “Scientific Assessment of NASA’s Mars Sample-Return Mission Options”). These include, among other high-priority objectives, the search for evidence of possible martian life. With regard to the general level of alternate mission option plans (i.e., baseline, paced, accelerated, or aggressive), COMPLEX believes that a vigorous, carefully planned, and well-executed program of martian exploration and sample return is warranted. However, the missions should address substantial scientific goals and not be overly focused on a single objective. In addition to comments on the principal objectives of martian exploration, COMPLEX’s assessment also offers observations and suggestions on implementation strategy, site selection, and sampling strategy, as well as technology requirements and related programmatic issues that the committee believes are essential for the success of any Mars sample-return program. The Space Studies Board and COMPLEX look forward to following the future development and implementation of NASA’s plans for Mars exploration and, in particular, sample-return missions. COMPLEX would look forward to hearing an updated presentation on NASA’s Mars planning activities and to receiving feedback on the comments contained in the attached assessment. Perhaps this could be done at the next COMPLEX meeting, scheduled for February 3–5, 1997, at the Jet Propulsion Laboratory. Signed by Claude R.Canizares Chair, Space Studies Board Ronald Greeley Chair, Committee on Planetary and Lunar Exploration

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Space Studies Board: Annual Report 1996 At its October 16–18, 1996, meeting, the Space Studies Board’s Committee on Planetary and Lunar Exploration (COMPLEX), chaired by Prof. Ronald Greeley (Arizona State University), conducted an assessment of the plans developed within NASA’s Mars Surveyor program office to meet the long-standing scientific goal of returning martian samples to Earth for study in terrestrial laboratories. This assessment was made at the request of Dr. Jurgen Rahe, NASA’s Science Program Director for Solar System Exploration, with a requested response date of early December, 1996. This assessment is based on material sent to committee members for review prior to the meeting,1 presentations by invited experts at the October meeting, and subsequent discussions in executive sessions. The goals of Mars sample-return missions and the types of scientific investigations that could be conducted on martian specimens in terrestrial laboratories were described by Drs. Bruce Jakosky (University of Colorado), Michael Drake (University of Arizona), Alan Treiman (Lunar and Planetary Institute), and Kenneth Nealson (University of Wisconsin, Milwaukee). The various mission scenarios currently being considered by NASA were described by Dr. Jeffrey Plescia (Jet Propulsion Laboratory). According to Dr. Plescia, NASA has outlined four sample return options, characterized as baseline, paced, accelerated, and aggressive (see appendix for details). The baseline option was described to COMPLEX at its June 1996 meeting by Dr. Daniel McCleese (Jet Propulsion Laboratory) of NASA’s Mars Surveyor program office. Because of the lack of details provided about the four proposed mission options (see appendix), COMPLEX must defer a specific assessment of mission plans. The committee can, however, make the following comments at this time regarding return of samples from Mars: It seems imprudent to land a 700-kg inert payload to simulate a sample-return vehicle, as planned in the baseline option. If appropriate instruments were identified, this opportunity could provide for the collection of scientific data. The paced and accelerated options both return what would appear to be scientifically valid samples, with earlier sample retrieval in the accelerated option. The aggressive option’s scientific potential is rich, but its scope seems unrealistically ambitious. Although COMPLEX is unable to make detailed comments on particular mission options at this time, it is able to provide observations and suggestions on implementation strategy, site selection and sampling strategy, technology requirements, and related programmatic issues. COMPLEX believes that close attention to these issues, highlighted in past National Research Council (NRC) reports, is essential for the success of Mars sample-return missions. OVERALL OBSERVATIONS In its 1996 report, Review of NASA’s Planned Mars Program,2 COMPLEX stated that “the goal of returning samples of martian soil, atmosphere, and, most importantly, rocks [should remain] a central element of NASA’s planning.” The scientific priorities for the study of Mars, as defined in past reports by COMPLEX, can be summarized as follows:3–5 Understanding the evolution of the planet’s surface and interior via studies of its chemistry, lithology, and morphology on a range of scales from local to global; Characterizing the dynamics and chemistry of the planet’s atmosphere and the degree to which climatic conditions have evolved over time; 1   Mars Expeditions Strategy Group, “The Search for Evidence of Life on Mars,” Jet Propulsion Laboratory, Pasadena, California, September 26, 1996. 2   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 26. 3   Space Studies Board, National Research Council, 1990 Update to Strategy for Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990, pp. 21–24. 4   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, pp. 61, 90, 93, 94, 96, 100, 117, 126, 129, and 132. 5   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, pp. 10–11.

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Space Studies Board: Annual Report 1996 Searching the planet for extinct or extant life, including evidence of the accumulation of a reservoir of prebiotic organic compounds and the extent of any subsequent prebiotic chemical evolution; and Determining the nature of the planet’s interaction with the solar wind and the extent to which these interactions affect the state and evolution of the planet’s upper atmosphere and ionosphere. Sample-return missions are relevant, if not essential, to addressing many of these goals. Therefore, the committee is pleased that NASA has taken the opportunity provided by the increased attention to Mars exploration resulting from the McKay et al. paper6 on the ALH84001 meteorite to accelerate planning of a program of Mars sample-return missions. Yet although findings by McKay et al. have captured the public’s interest, much as they have the attention of scientists, they are only suggestive. The existence of microfossils and other indicators of life in martian meteorites is far from proven and is currently the subject of intense study. Therefore, COMPLEX believes that it is inappropriate to predicate an important aspect of future martian studies on the unconfirmed results described in a single scientific paper. Rather, the appropriate scientific context within which NASA should frame its study of the possibility that life arose on Mars at some time in the past has several elements: the suggestive results from ALH84001, new findings on microbial life in extreme terrestrial environments (e.g., deep beneath Earth’s crust and oceans), new perspectives on the origin of terrestrial life, current understanding of the evolution of the martian and other planetary environments, and recent findings about the existence of planets around other stars. COMPLEX agrees with many of the elements in the working paper drafted by NASA’s Mars Expeditions Strategy Group,7 as noted below. However, given the framework for martian studies outlined above, COMPLEX urges that other considerations be incorporated into the program as discussed and summarized in the following sections. Prime among COMPLEX’s concerns is the inadvisability of NASA’s seeking only a simple answer to the question of life on Mars, because unequivocal evidence may be hard to find. The full implications of such a question can be realized only in the context of life’s origin in a planetary environment and of its subsequent evolution in conjunction with the evolution of the planet. COMPLEX,8–10 the Space Studies Board’s (SSB’s) former Committee on Planetary Biology and Chemical Evolution,11 and a recent NASA report12 have each outlined a consistent strategy for the exobiologic exploration of Mars. The results from ALH84001 do not, in COMPLEX’s opinion, invalidate the measured approach embodied in this strategy. On the contrary, while a suite of missions that exclusively address exobiology questions could advance the overall goals for the exploration of Mars, they could just as easily compromise future studies of Mars if the missions and their objectives are misconstrued. For example, if the single objective of sample-return missions is to resolve the question of life on Mars, then highly successful missions could be characterized as failures if they do not return microfossils or living organisms. Therefore, justification of missions in terms of their bearing on the question of martian life alone would be a disservice to the scientific community and to the public, and would have a detrimental impact on the potential scientific results for exobiology and the other planetary science disciplines. Consequently, NASA should focus its Mars program, and sample-return missions in particular, on the more comprehensive goal of understanding Mars as a possible abode of life, a goal that is fully compatible with previous recommendations. 6   D.McKay et al., “Search for Past Life on Mars: Possible Relict Biogenic Activity in Martian Meteorite ALH84001,” Science, August 16, 1996, p. 924. 7   Mars Expeditions Strategy Group, “The Search for Evidence of Life on Mars,” Jet Propulsion Laboratory, Pasadena, California, September 26, 1996. 8   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 10. 9   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, pp. 90–91. 10   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 61. 11   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, p. 76. 12   Exobiology Program Office, Exobiological Strategy for Mars Exploration, NASA, Washington, D.C., 1995.

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Space Studies Board: Annual Report 1996 STRATEGY ISSUES The search for life on Mars is only a part of the exobiologic study of the planet and of the scientific rationale for sample-return missions.13–16 Even if there is neither extant nor extinct life on Mars, the planet’s “prebiotic” chemical evolution is an important part of the history of life in the solar system.17,18 Study of the “prebiotic Mars” will provide a context for the possible occurrence of martian life and should be a fundamental part of the Mars sample-return program. With respect to life, Mars may provide access to a paleochemical record unavailable on Earth. COMPLEX recognizes that the overall structure of the Mars sample-return and exploration program should be outlined early. However, as noted previously,19 adaptability and flexibility of the program are of paramount importance. There should be sufficient flexibility in the program to allow later missions to take advantage of the results of earlier missions. Global reconnaissance of Mars should be a high priority early in the Mars sample-return program in order to allow intelligent selection of sample collection sites and to provide a global context for analysis of sample data.20,21 Such reconnaissance is planned from the Mars Global Surveyor (MGS); if that or subsequent orbital missions are not successful, however, pertinent measurements (such as high-resolution imaging and infrared spectroscopy from MGS) need to be obtained at the earliest opportunity. The Mars sample-return program neither begins with sample collection nor ends with the return of martian samples to Earth. The Mars Surveyor program must, for example, maintain a vigorous science analysis program during and following mission activity. Sufficient resources need to be allocated within the program for timely analysis of the data returned from the spacecraft already at Mars and/or related programs such as the development of appropriate instrumentation, and for study of samples in terrestrial laboratories. Planetary protection requirements should be defined as early in the program as is feasible. These requirements will ultimately determine the time scale regarding the availability of samples for analysis in terrestrial laboratories. The SSB’s Task Group on Issues in Sample Return is currently investigating these topics and related issues, such as the role of regulatory agencies and public perception of the risk associated with sample-return missions.22 ISSUES REGARDING SELECTION OF SAMPLE-RETURN SITES Selection of samples to be returned to Earth must be optimized in order to provide the best opportunities for learning as much as possible about Mars. For example, the sampling mechanism could have the ability to discard a previously selected specimen should a more interesting one be found. Randomly selected rocks or sediments, even 13   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 10. 14   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 104. 15   Space Studies Board, National Research Council, 1990 Update to Strategy for Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990, p. 5. 16   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, p. 91. 17   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, pp. 10–11. 18   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, p. 77. 19   Mars Expeditions Strategy Group, “The Search for Evidence of Life on Mars,” Jet Propulsion Laboratory, Pasadena, California, September 26, 1996, p. 5. 20   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 22. 21   Space Studies Board, National Research Council, 1990 Update to Strategy for Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990, p. 24. 22   Space Studies Board, National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1996, in preparation.

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Space Studies Board: Annual Report 1996 from interesting sites, are unlikely to be adequate samples for exobiologic analysis.23–25 Similarly, landing sites for sample-return missions should be selected on the basis of scientific potential rather than engineering constraints alone. The future flexibility of the program should be provided for by identifying a diversity of sites early. The report of NASA’s Mars Expeditions Strategy Group26 identifies three broad environments as potential sample-return sites. These are sites associated with ancient ground water, ancient surface water, and modern ground water. Recognizing that current knowledge of martian geology and geochemistry derives primarily from Viking data, new information from near-term missions, such as Mars Global Surveyor, should have a significant impact on final site selection if adequate resources are provided for data analysis. The set of sites selected should represent different geologic environments relevant to the several objectives of a balanced program of Mars exploration.27 In this regard, the ancient ground water site and the ancient aqueous environment appear to be well chosen. Sites should be selected where the relevant geologic record is best preserved and most easily studied. The physical and chemical conditions necessary for the origin and early development of life are unknown, even on Earth. As noted in past NRC documents,28–30 locating relevant sites is dependent on data collected from prior missions, and a broad-based study of Mars is essential to this process. Sites defined to provide maximum information on the physical and chemical conditions early in martian history are especially important, because early conditions are most likely to be relevant to the origin and early evolution of life. Of the two ancient sites, the ground water (highland) site is probably the better choice for the first sample-return mission because older, possibly more diverse, materials should be present. TECHNOLOGY DEVELOPMENT The capability should be developed for significant mobility (tens of kilometers) to allow sampling of a diverse suite of rocks from a landing site.31–33 The probability of making significant advances in exobiologic investigations depends critically on the quality of the material returned, and increased mobility provides the capability to examine numerous samples before a final selection is made. This capability would greatly enhance the collection of an optimal suite of returned samples, as well as permit a detailed characterization of the environmental context of a site. A broad suite of capable, miniature instruments for in situ determination of the geomorphology, mineralogy, petrology, and chemistry of a site should be developed.34,35 These instruments will aid in sample selection and determination of the environmental context of samples. The suite of instruments developed should cover the range 23   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 23. 24   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 104. 25   Space Science Board, National Research Council, Post-Viking Biological Investigations of Mars, National Academy of Sciences, Washington, D.C., 1977, pp. 14 and 23. 26   Expeditions Strategy Group, “The Search for Evidence of Life on Mars,” Jet Propulsion Laboratory, Pasadena, California, September 26, 1996, p. 2. 27   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 10. 28   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, pp. 10–11. 29   Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995–2010, National Academy Press, Washington, D.C., 1994, p. 103. 30   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, pp. 88–89. 31   Space Science Board, National Research Council, Strategy for Exploration of the Inner Planets: 1977–1987, National Academy of Sciences, Washington, D.C., 1978, p. 44. 32   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, p. 93. 33   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 23. 34   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, p. 93. 35   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 25.

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Space Studies Board: Annual Report 1996 of currently feasible, as well as anticipated, measurement techniques to permit flexibility in instrument selection and to respond to new discoveries. Methods should be developed for landing close to surface target sites. The size of the major axis of the landing-error ellipse should be smaller than the range of the rovers. This capability will allow complex geologic sites to be targeted safely and within reach of rovers. Examples of potentially interesting sites include volcanic systems, sedimentary basins, or channel floors, walls, and ejecta deposits.36,37 Development of high-spatial-resolution (centimeter to meter) instruments and platforms to extend the global characterization of rock and soil materials to scales appropriate for lander and rover operations should be pursued.38 These data should be available in time for site selection and return of samples. It can be argued that sampling techniques should be developed to optimize the mass of the returned samples, to reach less-weathered material in the interior of rocks, and to sample at depth.39 Natural processes, such as impacts, may have exposed rocks and material from depth, but innovative technologies may still be needed to obtain samples suitable for meeting the scientific objectives of any given mission. The ubiquitous, superoxidizing material covering the martian surface material may, however, obviate such requirements for unweathered samples. Even so, technologies to allow sample manipulation for selection and subsampling of large fragments will be important because of the constraints on sample-return mass. Sample handling and return technologies necessary to satisfy planetary protection requirements and to preserve samples in a pristine state should be developed in a timely manner, according to previous reports.40,41 These topics are currently under consideration by the SSB’s Task Group on Issues in Sample Return (TGISR). COMPLEX defers additional consideration of these topics until after the publication of TGISR’s report.42 RELATED WORK Criteria need to be developed for the unambiguous identification of biotic signatures. The ALH84001 meteorite illustrates the need to distinguish between biotic and abiotic mechanisms at the nanometer scale.43 Terrestrial laboratory studies and field work are required to understand the chemical signatures in soils and rocks affected by living organisms as well as those caused by purely chemical means. In the former case, there is a need to understand better the diversity of organisms and environments, and their interaction at the microbiological scale. In the latter case, there is a need to know more about the redox chemistry, isotope fractionation, mineralogy, and physiochemical processes that mimic or preceded life. The goal is to be able to distinguish in a definitive manner between biotic and abiotic processes in ancient environments, in particular by analysis of meteorite samples found on Earth as well as samples returned directly from Mars. Previous studies44,45 have discussed in detail some of these experimental procedures. However, ALH84001 provides an important example of current procedures and limitations to address exobiologic questions. In order to arrive at definitive results regarding life and its origins using small samples, specialized equipment and laboratories will be required. 36   Space Studies Board, National Research Council, Biological Contamination of Mars: Issues and Recommendations, National Academy Press, Washington, D.C., 1992, pp. 51 and 53. 37   Space Science Board, National Research Council, Space Science in the Twenty-First Century, National Academy Press, Washington, D.C., 1988, p. 104. 38   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 22. 39   Space Studies Board, National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, p. 23. 40   Space Studies Board, National Research Council, Biological Contamination of Mars: Issues and Recommendations, National Academy Press, Washington, D.C., 1992. 41   Space Science Board, National Research Council, Strategy for Exploration of the Inner Planets: 1977–1987, National Academy of Sciences, Washington, D.C., 1978, p. 50. 42   Space Studies Board, National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1996, in preparation. 43   D. McKay et al., “Search for Past Life on Mars: Possible Relict Biogenic Activity in Martian Meteorite ALH84001,” Science, August 16, 1996, p. 924. 44   Space Studies Board, National Research Council, The Search for Life’s Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990, p. 77. 45   Space Science Board, National Research Council, Strategy for Exploration of the Inner Planets: 1977–1987, National Academy of Sciences, Washington, D.C., 1978, pp. 44–56.

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Space Studies Board: Annual Report 1996 Research on related antarctic meteorites should be improved. The collection of additional martian meteorites will be useful for putting the ALH84001 results into a broader context and for additional studies of evidence of past life or prebiotic materials from Mars. The rate of collection could, according to several past participants in the Antarctic Search for Meteorites (ANSMET) program, be increased if, for example, field-collection procedures in Antarctica are made more efficient by eliminating excessive requirements for documenting sample locations. Tests have demonstrated that equipping ANSMET teams with Global Positioning System receivers would allow precise determination of locations, without taking much time away from sample collection. SUMMARY RECOMMENDATIONS In summary, COMPLEX believes that whether or not the results of McKay et al. are confirmed, the measured approach to the exploration of Mars advocated by COMPLEX and other groups is the optimum strategy for advancing our understanding of Mars on all fronts. Moreover, the committee is guardedly optimistic that NASA’s current planning for Mars sample-return missions will be consistent with the priorities outlined in past NRC reports, provided that NASA takes into account the issues discussed above, as summarized here: Formulate a program of Mars sample-return missions in the context of recent developments in the planetary, life, and astronomical sciences and directed toward the comprehensive goal of understanding Mars as a possible abode of life. Incorporate previously developed strategies for determining “prebiotic” chemical evolution into the Mars sample-return program. Maintain adaptability and flexibility in the Mars sample-return program to take into account possible new discoveries from ongoing Mars missions. Ensure that the global reconnaissance of Mars is implemented as early as possible. Ensure that sites and samples are selected that are consistent with established strategies for exobiology and martian exploration. To understand the results from each mission and to provide input for the planning of ongoing missions during the entire Mars exploration program, there must be an adequate, ongoing data-analysis program. Ensure that sample handling strategies, including planetary protection issues, are judiciously formulated and implemented. Develop the capability for achieving long-range (tens of kilometers) mobility and high-precision landing. Develop a broad suite of capable, miniature instruments for in situ measurements of surface properties relevant to exobiology and general martian exploration. Develop the criteria to enable the unambiguous identification of biotic signatures. Increase the rate of collection of antarctic meteorites relevant to Mars by, for example, increasing the efficiency of field collection procedures.